OSTEOLOGY OF THE HORSE. 71 



wise. It passes onward, covering and connecting- the remaining 

 superior spines of the back, and also those of the loins, sacrum, 

 and coccyx, growing upon the last bone gradually smaller and 

 smaller, and ultimately vanishing upon its extremity. Being 

 highly elastic, it will admit of all the motions the spine is suscep- 

 tible of; while it has a continual tendency to maintain or recover 

 its original or natural form. 



Articulations of the thorax. — The vertebral extremity 

 of the rib forms three distinct and separate joints with the spine, 

 and is further maintained by two ligaments:— 1st, Capsular mem- 

 brane of the head, in its attachment surrounds and includes the 

 whole of the head ; but sends ofJ'a process, internally, by which 

 the surface opposed to one vertebra is formed into a synovial ca- 

 vity, distinct from that which is adapted to the other vertebra, 

 next to it. This part of the union is strengthened by some liga- 

 mentous fibres which spring from the summit of the head ; 2d, 

 Capsular membrane of the tubercle, surrounds the process at its 

 articulation with the transverse process of the vertebree; 3d, Ex- 

 ternal ligament, fixing the neck of the rib to the spine, exter- 

 nally ; 4th, Internal ligament, a similar one, internally. 



The cartilages of the true ribs, which are attached immediately 

 to the sternum, are received into the cups in the lateral borders 

 of that bone, and maintained there by — 1st, Ligamentous ex- 

 pansions, radiating from the surfaces, both superior and inferior, 

 of the sternum to their extremities; 2d, Capsular membranes, 

 inclosing the extremities within their sockets. 



The several portions of the sternum are united, one to another, 

 by fibro'Cartilaginous interpositions ; and their union is strength- 

 ened by the ligamentary expansions upon the surface, internal as 

 well as external. The anterior bone is surmounted by a cartilage 

 of considerable breadth, which extends in a curvature upwards, 

 not unlike the form of the keel of a ship ; hence it has got the 

 name of the cariniform cartilage. 



Articulations of the pelvis. — The sacro-vertehral arti- 

 culation, formed between the last lumbar vertebra and the base 

 of the sacrum, consists — 1st, of an inter-vertebral substance 

 in the middle, similar to what exists in the spine; 2dly, of two 

 superior transverse ligaments, affixed to the transverse processes; 

 and, 3dly, of two inferior transverse ligaments, which run from 

 the fourth and fifth transverse processes of the loins to the crista 

 of the ileum. — 'The sacro-iliac articulations are formed by the in- 

 terposition of fibro-cartilaginous substances between the trans- 

 verse processes of the sacrum and the venters of the ileum, resting 

 upon them ; and is strengthened by ligamentary bands passing 

 from the posterior spines and borders of the ileum to the trans- 



